Periodontal diseases are one of the most common bacterial infections of humans and impose a significant burden on the health care system. One of the predominant pathogens in periodontal disease is P. gingivalis; however, P. gingivalis can also inhabit the oral cavity in the absence of disease. The interaction between P. gingivalis and gingival epithelial cells makes a significant contribution to the degree of equilibrium between host and microbe, and to overall gingival health status. P. gingivalis can manipulate epithelial cell signal transduction pathways in order to direct entry into the host cell and to reprogram host innate immunity. One of the effector molecules of P. gingivalis is the HAD family serine phosphatase, SerB. The goal of this proposal is define the outcomes of the interaction between P. gingivalis and gingival epithelial cells as they relate colonization of the organism and the generation of immune dysbiosis. We shall also continue our major focus on the role of the functionally versatile SerB invasin and modulin of P. gingivalis. Cofilin, an actin depolymerizing protein, is required for P. gingivalis invasion. We will examine the ability of SerB to dephosphorylate and inactivate LIMK kinase which will lead to activation of cofilin. We will then investigate the impact of P. gingivalis on ROCK, PAK1 and MK2 pathways that lead to activation of LIMK. These interactions will be observed within the cell by live cell imaging. P..gingivalis can suppress IL-8 production in part through regulation of actin dynamics. We shall study the cofilin dependent, actin mediated suppression of IL-8 by P. gingivalis. The immune disruptive ability of P. gingivalis also extends to T-cell chemokines, and the mechanism of suppression of IP-10, ITAC and Mig will be studied. We will also begin to assess biological relevance by examining T-cell migration in response to epithelial cells infected with P. gingivalis. These studies will provide a detailed molecular analysis of the targeting of host signal transduction by P. gingivalis along with the role of a specific effector phosphatase. Ultimately, the knowledge gained could be developed into strategies that could be utilized to intervene in the P. gingivalis-epithelial cell interaction to ensure that the outcome is non-harmful to the host. RELEVANCE (See instructions): P. gingivalis is a cause of periodontal diseases that afflict millions of Americans. In this study we will examine the interactions between P. gingivalis and the human cells that are colonized by the organism. The information to be gathered could be used to identify targets for novel therapeutic agents designed to interfere with the colonization and survival strategies of P. gingivalis.